#include <bits/stdc++.h>
using namespace std;

using u32 = unsigned int;
using i64 = long long;
using u64 = unsigned long long;

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    int test;
    cin >> test;
    while (test--) {
        int n, m;
        cin >> n >> m;
        int res = 1 << 30;
        for (int i = 0; i < n; ++i) {
            int x, y;
            cin >> x >> y;
            res = min(res, ((m - 1) / x + 1) * y);
        }
        cout << res << '\n';
    }
}